Documentation ¶
Overview ¶
Package imageproxy provides an image proxy server. For typical use of creating and using a Proxy, see cmd/imageproxy/main.go.
Index ¶
Constants ¶
This section is empty.
Variables ¶
var NopCache = new(nopCache)
NopCache provides a no-op cache implementation that doesn't actually cache anything.
Functions ¶
Types ¶
type Cache ¶ added in v0.2.1
type Cache interface { // Get retrieves the cached data for the provided key. Get(key string) (data []byte, ok bool) // Set caches the provided data. Set(key string, data []byte) // Delete deletes the cached data at the specified key. Delete(key string) }
The Cache interface defines a cache for storing arbitrary data. The interface is designed to align with httpcache.Cache.
type Options ¶ added in v0.2.1
type Options struct { // See ParseOptions for interpretation of Width and Height values Width float64 Height float64 // If true, resize the image to fit in the specified dimensions. Image // will not be cropped, and aspect ratio will be maintained. Fit bool // Rotate image the specified degrees counter-clockwise. Valid values // are 90, 180, 270. Rotate int FlipVertical bool FlipHorizontal bool // Quality of output image Quality int // HMAC Signature for signed requests. Signature string // Allow images to scale beyond their original dimensions. ScaleUp bool }
Options specifies transformations to be performed on the requested image.
func ParseOptions ¶ added in v0.2.1
ParseOptions parses str as a list of comma separated transformation options. The following options can be specified in any order:
Size and Cropping ¶
The size option takes the general form "{width}x{height}", where width and height are numbers. Integer values greater than 1 are interpreted as exact pixel values. Floats between 0 and 1 are interpreted as percentages of the original image size. If either value is omitted or set to 0, it will be automatically set to preserve the aspect ratio based on the other dimension. If a single number is provided (with no "x" separator), it will be used for both height and width.
Depending on the size options specified, an image may be cropped to fit the requested size. In all cases, the original aspect ratio of the image will be preserved; imageproxy will never stretch the original image.
When no explicit crop mode is specified, the following rules are followed:
- If both width and height values are specified, the image will be scaled to fill the space, cropping if necessary to fit the exact dimension.
- If only one of the width or height values is specified, the image will be resized to fit the specified dimension, scaling the other dimension as needed to maintain the aspect ratio.
If the "fit" option is specified together with a width and height value, the image will be resized to fit within a containing box of the specified size. As always, the original aspect ratio will be preserved. Specifying the "fit" option with only one of either width or height does the same thing as if "fit" had not been specified.
Rotation and Flips ¶
The "r{degrees}" option will rotate the image the specified number of degrees, counter-clockwise. Valid degrees values are 90, 180, and 270.
The "fv" option will flip the image vertically. The "fh" option will flip the image horizontally. Images are flipped after being rotated.
Quality ¶
The "q{qualityPercentage}" option can be used to specify the quality of the output file (JPEG only)
Examples
0x0 - no resizing 200x - 200 pixels wide, proportional height 0.15x - 15% original width, proportional height x100 - 100 pixels tall, proportional width 100x150 - 100 by 150 pixels, cropping as needed 100 - 100 pixels square, cropping as needed 150,fit - scale to fit 150 pixels square, no cropping 100,r90 - 100 pixels square, rotated 90 degrees 100,fv,fh - 100 pixels square, flipped horizontal and vertical 200x,q80 - 200 pixels wide, proportional height, 80% quality
type Proxy ¶ added in v0.2.1
type Proxy struct { Client *http.Client // client used to fetch remote URLs Cache Cache // cache used to cache responses // Whitelist specifies a list of remote hosts that images can be // proxied from. An empty list means all hosts are allowed. Whitelist []string // Referrers, when given, requires that requests to the image // proxy come from a referring host. An empty list means all // hosts are allowed. Referrers []string // DefaultBaseURL is the URL that relative remote URLs are resolved in // reference to. If nil, all remote URLs specified in requests must be // absolute. DefaultBaseURL *url.URL // SignatureKey is the HMAC key used to verify signed requests. SignatureKey []byte // Allow images to scale beyond their original dimensions. ScaleUp bool }
Proxy serves image requests.
Note that a Proxy should not be run behind a http.ServeMux, since the ServeMux aggressively cleans URLs and removes the double slash in the embedded request URL.
type Request ¶ added in v0.2.1
type Request struct { URL *url.URL // URL of the image to proxy Options Options // Image transformation to perform Original *http.Request // The original HTTP request }
Request is an imageproxy request which includes a remote URL of an image to proxy, and an optional set of transformations to perform.
func NewRequest ¶ added in v0.2.1
NewRequest parses an http.Request into an imageproxy Request. Options and the remote image URL are specified in the request path, formatted as: /{options}/{remote_url}. Options may be omitted, so a request path may simply contian /{remote_url}. The remote URL must be an absolute "http" or "https" URL, should not be URL encoded, and may contain a query string.
Assuming an imageproxy server running on localhost, the following are all valid imageproxy requests:
http://localhost/100x200/http://example.com/image.jpg http://localhost/100x200,r90/http://example.com/image.jpg?foo=bar http://localhost//http://example.com/image.jpg http://localhost/http://example.com/image.jpg
type TransformingTransport ¶ added in v0.2.1
type TransformingTransport struct { // Transport is the underlying http.RoundTripper used to satisfy // non-transform requests (those that do not include a URL fragment). Transport http.RoundTripper // CachingClient is used to fetch images to be resized. This client is // used rather than Transport directly in order to ensure that // responses are properly cached. CachingClient *http.Client // Proxy is used to access command line flag settings during roundtripping. Proxy *Proxy }
TransformingTransport is an implementation of http.RoundTripper that optionally transforms images using the options specified in the request URL fragment.
Directories ¶
Path | Synopsis |
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cmd
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imageproxy
imageproxy starts an HTTP server that proxies requests for remote images.
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imageproxy starts an HTTP server that proxies requests for remote images. |